Synthesis of nitrogen-doped micro-mesoporous carbon nanospheres for enhanced CO2 absorption

Nitrogen-doped micro-mesoporous carbon nanospheres are considered as promising CO₂ adsorbents due to their remarkable efficiency and cost-effectiveness. In this work, nitrogen-doped micro-mesoporous carbon nanospheres were constructed, during which soft micelles (triblock copolymer P123) and a hard template (silica sol) as structural precursors were employed, and urea was used as the nitrogen source and KHCO₃ as the chemical activator. Through a combined chemical activation and post-doping strategy, ultra-micropores were successfully introduced into the carbon framework alongside rich nitrogen doping. The final nitrogen-doped micro-mesoporous carbon nanospheres exhibit high specific surface areas (529–2225 m²/g) and nitrogen contents ranging from 2.20 wt% to 6.02 wt%. The optimal sample, NMCNs-2K2U800, demonstrates excellent CO₂ adsorption performance, with capacities of 7.86 mmol/g at 0 ℃ and 4.31 mmol/g at 25 ℃ under 1 bar. This study systematically investigates the effects of activator and nitrogen source on the pore structure, nitrogen speciation, and CO₂ adsorption behavior of carbon materials. Further, a viable strategy for the controlled synthesis of porous carbons and providing valuable insights into the design of high-performance CO₂ adsorbents is provided.